A display device forming a screen for liquid crystal televisions, tablet terminals, portable information terminals called smart phones, and the like is manufactured using a glass substrate and secured in a casing. Normally, these types of display devices are not intended for use by bending and folding. However, flexible display devices that may be bent and folded are expected to develop new uses not found in conventional products. For example, in the specifications of Japanese Laid-Open Patent Publication Number 2012-238005, Japanese Laid-Open Patent Publication Number 2015-2177, and U.S. Patent Application Publication Number 2016/0174304, a flexible display device manufactured using a thin plastic film is disclosed.